The present invention is applicable to any type of aqueous stream or effluent and provides generally an apparatus and methodology for visually determining the presence of oily contaminants suspended or dispersed in an aqueous stream. The issues associated with marine bilgewater discharge which are presented in detail herein provide an excellent specific illustration of an environment to which the broader present invention is applicable. Over the past two decades, U.S. regulations dealing with bilgewater discharge for all types of vessels have grown increasingly stringent. Environmental technology has struggled to keep pace but until recently, no removal method has been capable of eliminating sheen and extracting substantially all harmful contaminants from bilgewater. Federal regulations set a high standard for bilgewater discharge, because even tiny amounts of bilgewater oil have been demonstrated to kill huge numbers of lobster eggs, which is just one example of the enormous threat to aquatic life.
The Federal Water Pollution Act, also known as the Clean Water Act, accordingly proscribes even the appearance of a visible sheen on the water, punishable by a $5,000 penalty. More specifically, the act “prohibits the discharge of oil or oily waste into or upon the navigable waters of the United States or the waters of the contiguous zone if such discharge causes a film or sheen upon, or causes a sludge or emulsion beneath the surface of the water.” From an environmental perspective, the increased regulatory activity in bilgewater discharge limits is warranted. The cumulative effect of vessels ranging from small recreational boats to large surface ships dumping even small amounts of bilgewater could wreak damage upon fragile aquatic ecosystems and likely has already done so.
In the instance of marine bilgewater discharge, the primary sources of the contaminants are vessel propulsion systems and auxiliary systems that use fuels, lubricants, hydraulic fluid, antifreeze, solvents and cleaning chemicals. Certain waste streams such as steam condensate, boiler blowdown, drinking fountain water, and sink drainage located in various machinery spaces can also drain to the bilge.
Currently, commercial and military surface ships primarily employ two different methods in dealing with bilgewater treatment and removal. Many of these vessels use oil-water separator systems to reduce the oil content of bilgewater prior to overboard discharge. Most of these large vessels also have onboard systems for collecting and transferring bilgewater to a holding tank for later removal and disposal on shore.
In the present inventor's U.S. Pat. No. 6,475,393 (see also related U.S. Pat. No. 6,180,010), it is disclosed that the compositions described in the inventor's U.S. Pat. Nos. 5,437,793; 5,698,139; and 5,837,146, and 5,961,823 (all of which disclosures are hereby incorporated by reference) have extremely strong affinities for the contaminants in oily bilgewater; and that when oily bilgewater streams containing these noxious contaminants are passed through filtration media incorporating these compositions, the contaminants are immobilized at the media. As a result, concentration levels of the contaminants in the filtrate may be reduced to very low values, in some instances below detectable limits in a single pass. This feature not only enables ready removal of oils, greases, and similar materials from the bilgewater, but also allows removal of pernicious, slightly soluble organic compounds such as benzene, toluene, xylene, halogenated hydrocarbons, ethoxylated glycols, and the like. These noxious contaminants are among the more difficult compounds to remove from water, and indeed most are carcinogenic. The solubility of the foregoing substances renders most prior art physical separation methods generally ineffective and causes formation of stable and pseudostable oily emulsions (micelle size of 400 micrometers or less), which also do not respond well to gravity separation due to neutral buoyancy.
In accordance with these prior patents, the bilgewater can be passed through one or more filters incorporating the principles of the earlier inventions, prior to the bilgewater being actually discharged from the vessel. The filter or filters may simply be placed directly in the bilgewater discharge line, for example, downstream of the bilgewater pump effecting the discharge flow. In a test of a typical such installation, the test results included removal of all sheen and visible discharge.
More specifically, the method of the prior invention may be described as one of passing the bilgewater through a fluid-pervious filtration media which has been infused with an absorption composition comprising a homogeneous thermal reaction product of an oil component selected from the group consisting of glycerides, fatty acids, alkenes, and alkynes, and a methacrylate or acrylate polymer component; the contaminant being thereby immobilized at the media. For convenience these absorption compositions may hereinafter be referred to as “MACs”, a term derived from “Mycelx absorbent compositions”, where “Mycelx” is not used as a technical descriptor but merely as a reference to the assignee of the aforementioned patents pertaining to the said compositions and methodology. It will be appreciated that the MACs used in the present invention are not limited to the specific absorption compositions disclosed in the aforementioned U.S. patents, but also may include for example, additional compositions falling within the aforementioned description of the compositions, such as improvements upon the previously patented compositions which yet remain within the technical description stated immediately above in this paragraph.
Filter configurations incorporating the MACs may be based on various water permeable substrates, such as shredded, spun or otherwise configured polypropylene or shredded or spun cellulose, which substrates are infused or otherwise treated with the absorbent compositions, which are then cured. These substrates may then be packed or otherwise disposed in a cartridge or canister filter, or the substrates can be formed into cured and infused bag filters which can be emplaced in canisters through which the contaminated bilgewater is flowed. Similarly, the said absorbent compositions can be incorporated into or upon other filtering substrates and media if desired, including for example, paper, compressed pulp materials, particulate porous foamed plastics, mineral particulates such as perlite and vermiculite, and particulate, fibrous or porous ceramic or porous (for example, sintered) metal substrates and media.
In the course of utilizing bilgewater filtration systems, including those based upon the foregoing principles, it is often difficult to determine the quality of effluent from oily water separators without relying on some detector response, sensor reading, or the like. Moreover, it is often not possible even to determine visually if such detectors are operating properly. The capability to perform a rapid visual inspection of a filtration system would be useful for quickly determining when the capacity of the filtration system has been exceeded. However, the inability to perform simple visual inspections has led to accidental oily bilge water discharge and can even lead to criminal prosecution of the individuals responsible. In the case of oily water treatment devices, it is not possible to effectively use transparent sight gauges or glass indicators on the housings or in the connecting piping, due to the tendency of the surfaces over which the discharge flows to become opaque from oily fouling. Difficulties such as this arise not only in bilgewater, but also in numerous aqueous process streams where it is at least equally important to be rapidly made aware of the presence of oily contaminants. The presence of oily contaminants can arise for many reasons other than filtration failure or overload, as for example from accidental or other unintended leakage of oily contaminants into the process stream.
Therefore, what is needed generally is an apparatus and/or method for visually determining the presence of oily contaminants, including those very small size oily droplet which may be present as or behave as particulates suspended or dispersed in an aqueous stream. More specifically, what is needed is a indicator device and method that allows for visually examining any aqueous stream to determine the presence therein of such contaminants. The capability to perform a rapid visual inspection of a filtration system would be useful for quickly determining when the capacity of any aqueous filtration system has been exceeded or when there has been any type of failure of the system. This may be particularly important in an industrial process arrangement that employs a bank of individual operating units connected in series and/or in parallel that share some commonality, in which a small oily discharge or leak in any individual unit is difficult to locate, but can be highly problematic.